As the method for molding a plastic lens for eyeglasses, an injection compression molding method using a thermoplastic resin such as a polycarbonate resin or a methacrylic resin is known. For example, Patent Document 1 discloses one example of such injection compression molding method. In this method, an attempt is made to suppress optical strain or lowering of profile irregularity which occurs due to the shrinkage of a resin by further compressing the resin filled in the cavities of a mold by injection.
Further, as the method for producing a plastic lens for eyeglasses, a method is known in which a lens is molded as a semi-finished product of which the thickness is larger than the thickness of a finished product, and this semi-finished product, which is called as the semi-finished lens, is then shaped into a final product in the post process.
This method is mainly used in the production of a progressive refractive power lens used for bifocal glasses. Many of progressive refractive power lenses are produced by a method in which a plurality of semi-finished lenses which is molded such that they have different optical shapes is prepared in advance, an appropriate lens is selected from these lenses according to the prescription made for a user, and the lens is processed in a final shape such that the prescription is satisfied.